A record number of travelers are expected to take to the skies this summer thanks to a rebounding economy.

U.S. airlines will carry 222 million passengers between June 1 and Aug. 31, topping the summer of 2007 when 217.6 million people flew, Airlines for America, the industry's trade and lobbying group, predicted Monday. That figure includes 31 million travelers on international flights, also a record.

On average, there will be 2.4 million passengers a day, 4.5 percent more than last summer.

After several years of limiting their expansion, U.S. airlines are now quickly adding more seats, including 4.6 percent more this summer. Those added seats are mostly the result of airlines flying larger planes and packing in extra rows to existing jets.

Those extra seats have given pause to some Wall Street analysts who worry that airlines might have to discount fares to fill them. That hasn't happened yet, but after years of steadily rising airfares, there is a tiny bit of relief for fliers this summer — $2.01 in savings to be exact.

The average roundtrip domestic ticket this summer, including taxes, now stands at $454, down less than a percent from last summer. Vacationers to Europe will fare better, with the average ticket down 3 percent to $1,619, about $50 less than last summer, according to the Airlines Reporting Corp., which processes ticket transactions for airlines and travel agencies.

Summer can be one of the most difficult times to fly. While airlines can plan days in advance for blizzards, it is hard to know exactly when a thunderstorm will roll through an airport, shutting down all baggage handling and flights. Add into that extremely crowded airports: 13 of the 15 busiest days to travel fall in the summer, according to the airline trade group.

Passengers on planes aren't going to have much spare space.

Last July, U.S. airlines sold a record 87.8 percent of seats on domestic flights, according to the Bureau of Transportation Statics. And that figure does include seats occupied by airline employees flying for free. In other words: virtually every seat was taken.